在 Spark 中展平行

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问题描述

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我正在使用 Scala 对 Spark 进行一些测试.我们通常读取需要像以下示例一样操作的json文件:

I am doing some testing for spark using scala. We usually read json files which needs to be manipulated like the following example:

test.json:

{"a":1,"b":[2,3]}

val test = sqlContext.read.json("test.json")

如何将其转换为以下格式:

How can I convert it to the following format:

{"a":1,"b":2}
{"a":1,"b":3}

推荐答案

可以使用explode函数:

scala> import org.apache.spark.sql.functions.explode
import org.apache.spark.sql.functions.explode


scala> val test = sqlContext.read.json(sc.parallelize(Seq("""{"a":1,"b":[2,3]}""")))
test: org.apache.spark.sql.DataFrame = [a: bigint, b: array<bigint>]

scala> test.printSchema
root
 |-- a: long (nullable = true)
 |-- b: array (nullable = true)
 |    |-- element: long (containsNull = true)

scala> val flattened = test.withColumn("b", explode($"b"))
flattened: org.apache.spark.sql.DataFrame = [a: bigint, b: bigint]

scala> flattened.printSchema
root
 |-- a: long (nullable = true)
 |-- b: long (nullable = true)

scala> flattened.show
+---+---+
|  a|  b|
+---+---+
|  1|  2|
|  1|  3|
+---+---+

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